/* eslint-disable no-undef */
// 1.加密解密方法使用：

// 1.加密
// const str = '124中文内容';
// const base = new Base64();
// const result = base.encode(str);
// //document.write(result);

// //2.解密
// const result2 = base.decode(result);
// document.write(result2);
// //2.加密、解密算法封装：

function Base64() {
	// private property
	const _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_'

	// public method for encoding
	this.encode = function(input) {
		let output = ''
		let chr1, chr2, chr3, enc1, enc2, enc3, enc4
		let i = 0
		input = _utf8_encode(input)
		while (i < input.length) {
			chr1 = input.charCodeAt(i++)
			chr2 = input.charCodeAt(i++)
			chr3 = input.charCodeAt(i++)
			enc1 = chr1 >> 2
			enc2 = ((chr1 & 3) << 4) | (chr2 >> 4)
			enc3 = ((chr2 & 15) << 2) | (chr3 >> 6)
			enc4 = chr3 & 63
			if (isNaN(chr2)) {
				enc3 = enc4 = 64
			} else if (isNaN(chr3)) {
				enc4 = 64
			}
			output = output +
				_keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
				_keyStr.charAt(enc3) + _keyStr.charAt(enc4)
		}
		return output
	}

	// public method for decoding
	this.decode = function(input) {
		let output = ''
		let chr1, chr2, chr3
		let enc1, enc2, enc3, enc4
		let i = 0
		input = input.replace(/[^A-Za-z0-9-_]/g, '')
		while (i < input.length) {
			enc1 = _keyStr.indexOf(input.charAt(i++))
			enc2 = _keyStr.indexOf(input.charAt(i++))
			enc3 = _keyStr.indexOf(input.charAt(i++))
			enc4 = _keyStr.indexOf(input.charAt(i++))
			chr1 = (enc1 << 2) | (enc2 >> 4)
			chr2 = ((enc2 & 15) << 4) | (enc3 >> 2)
			chr3 = ((enc3 & 3) << 6) | enc4
			output = output + String.fromCharCode(chr1)
			if (enc3 != 64) {
				output = output + String.fromCharCode(chr2)
			}
			if (enc4 != 64) {
				output = output + String.fromCharCode(chr3)
			}
		}
		output = _utf8_decode(output).replace('\u0000', '')
		return output
	}

	// private method for UTF-8 encoding
	// eslint-disable-next-line camelcase
	const _utf8_encode = function(string) {
		string = string.replace(/\r\n/g, '\n')
		let utftext = ''
		for (let n = 0; n < string.length; n++) {
			const c = string.charCodeAt(n)
			if (c < 128) {
				utftext += String.fromCharCode(c)
			} else if ((c > 127) && (c < 2048)) {
				utftext += String.fromCharCode((c >> 6) | 192)
				utftext += String.fromCharCode((c & 63) | 128)
			} else {
				utftext += String.fromCharCode((c >> 12) | 224)
				utftext += String.fromCharCode(((c >> 6) & 63) | 128)
				utftext += String.fromCharCode((c & 63) | 128)
			}
		}
		return utftext
	}
	// private method for UTF-8 decoding
	// eslint-disable-next-line camelcase
	const _utf8_decode = function(utftext) {
		let string = ''
		let i = 0
		let c = 0
		let c2 = 0
		let c3 = 0
		while (i < utftext.length) {
			c = utftext.charCodeAt(i)
			if (c < 128) {
				string += String.fromCharCode(c)
				i++
			} else if ((c > 191) && (c < 224)) {
				c2 = utftext.charCodeAt(i + 1)
				string += String.fromCharCode(((c & 31) << 6) | (c2 & 63))
				i += 2
			} else {
				c2 = utftext.charCodeAt(i + 1)
				c3 = utftext.charCodeAt(i + 2)
				string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63))
				i += 3
			}
		}
		return string
	}
}
export default Base64